Macrostructures of porous inorganic material and process for their preparation

ABSTRACT

There is provided macrostructures of porous inorganic material which can have controlled size, shape, and/or porosity and a process for preparing the macrostructures. The macrostructures comprise a three-dimension network of particles of porous inorganic materials. The process for preparing the macrostructures involves forming an admixture containing a porous organic ion exchanger and a synthesis mixture capable of forming the porous inorganic material and then converting the synthesis mixture to the porous inorganic material. After formation of the composite material, the porous organic ion exchanger can be removed from the composite material to obtain the macrostructures.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.______ (not yet assigned) [attorney docket no. 99B011], filed May 17,1999, and entitled “Process for Production of Macrostructures of aMicroporous Material”.

FIELD OF THE INVENTION

The present invention concerns macrostructures of mesoporous inorganicmaterial and microporous inorganic material which can have controlledsize, shape, and/or porosity and a process for production of themacrostructures.

BACKGROUND OF THE INVENTION

Both mesoporous inorganic material and microporous inorganic materialare characterized by a large specific surface area in pores and are usedin a large number of applications of considerable commercial importance.The terms “porous inorganic material” and “porous material”, as usedherein, includes mesoporous inorganic material, microporous inorganicmaterial, and mixtures thereof.

In most of the applications using porous inorganic material, the factthat the phase interface between the solid porous material and themedium (liquid or gas) in which it is used is large can be veryimportant. Heterogeneous phase catalysts used in refinery processes,petrochemical conversion processes, and different environmentallyrelated applications often comprise porous inorganic material,especially microporous material. Adsorbents for the selective adsorptionin the gas or liquid phase or the selective separation of ioniccompounds are often porous inorganic material. In addition to theseapplications, porous inorganic materials have recently becomeincreasingly utilized in a number of more technologically advancedareas. Examples of such uses include use in chemical sensors, in fuelcells and batteries, in membranes for separation or catalytic purposes,during chromatography for preparative or analytical purposes, inelectronics and optics, and in the production of different types ofcomposites.

Although a large phase interface is often a fundamental requirement foruse of porous materials in different applications, a number ofadditional requirements related to the specific area of application areimposed on these materials. For example, the large phase interfaceavailable in the pores of the porous organic material must be accessibleand useable. Therefore, the porosity, pore size and pore sizedistribution in large pores (meso- and macropores) are often of majorsignificance, especially when mass transport affects processperformance. The surface properties of the porous material can also bevery important for the performance of the material in a givenapplication. In this context, the purity of the material is alsosignificant. In most applications, size and shape of porousmacrostructures containing the porous inorganic material and the degreeof variation of these properties are very important. During use, thesize and shape of the porous macrostructures can influence propertieslike mass transport within the porous structures, pressure drop over abed of particles of the material, and the mechanical and thermalstrength of the material. The factors that are the most important willvary depending on the application in which the macrostructures are usedas well as the configuration of the process in which the applicationoccurs. Techniques that permit production of a material with increasedspecific surface area, pore structure (pore size/pore sizedistribution), chemical composition, mechanical and thermal strength, aswell as increased and uniform size and shape, are consequently requiredto tailor porous inorganic macrostructures to different applications.

Mesoporous inorganic materials include amorphous metal oxide(non-crystalline) materials which have mesoporous and optionallypartially microporous structure. The pore size of the mesoporousinorganic material is usually in the range of from about 20 Å to about500 Å.

Microporous inorganic materials include crystalline molecular sieves.Molecular sieves are characterized by the fact that they are microporousmaterials with pores of a well-defined size in the range of from about 2Å to about 20 Å. Most molecules, whether in the gas or liquid phase,both inorganic and organic, have dimensions that fall within this rangeat room temperature. Selecting a molecular sieve with a suitable poresize therefore allows separation of a molecule from a mixture throughselective adsorption, hence the name “molecular sieve”. Apart from theselective adsorption and selective separation of uncharged seeds, thewell-defined pore system of the molecular sieve enables selective ionexchange of charged seeds and selective catalysis. In the latter twocases, significant properties other than the micropore structureinclude, for instance, ion exchange capacity, specific surface area andacidity.

Molecular sieves can be classified into various categories such as bytheir chemical composition and their structural properties. A group ofmolecular sieves of commercial interest is the group comprising thezeolites, that are defined as crystalline aluminosilicates. Anothergroup is that of the metal silicates, structurally analogous tozeolites, but for the fact that they are substantially free of aluminum(or contain only very small amounts thereof). Still another group ofmolecular sieves are ALPO-based molecular sieves which contain frameworktetrahedral units of alumina (AlO₂) and phosphorous oxide (PO₂) and,optionally, silica (SiO₂). Examples of such molecular sieves includeSAPO, ALPO, MeAPO, MeAPSO, ELAPO, and ELAPSO.

A summary of the prior art, in terms of production, modification andcharacterization of molecular sieves, is described in the book MolecularSieves—Principles of Synthesis and Identification (R. Szostak, BlackieAcademic & Professional, London, 1998, Second Edition). In addition tomolecular sieves, amorphous materials, chiefly silica, aluminum silicateand aluminum oxide, have been used as adsorbents and catalyst supports.A number of long-known techniques, like spray drying, prilling,pelletizing and extrusion, have been and are being used to producemacrostructures in the form of, for example, spherical particles,extrudates, pellets and tablets of both micropores and other types ofporous materials for use in catalysis, adsorption and ion exchange. Asummary of these techniques is described in Catalyst Manufacture, A. B.Stiles and T. A. Koch, Marcel Dekker, New York, 1995.

Because of limited possibilities with the known techniques, considerableinvestment has been made to find new ways to produce macrostructures ofporous inorganic materials, with a certain emphasis on those in the formof films.

PCT Publication WO 94/25151 involves the production of films ofmolecular sieves by a process in which seed crystals of molecular sievesare deposited on a substrate surface and then made to grow together intoa continuous film. PCT Publication WO 94/25152 involves the productionof films of molecular sieves by introduction of a substrate to asynthesis solution adjusted for zeolite crystallization andcrystallization with a gradual increase in synthesis temperature. PCTPublication WO 94/05597 involves the production of colloidal suspensionsof identical microparticles of molecular sieves with an average sizebelow 200 nm. PCT Publication WO 90/09235 involves method for productionof an adsorbent material in the form of a monolith by impregnation ofthe monolithic cell structure with a hydrophobic molecular sieve,followed by partial sintering of the molecular sieve with the materialfrom which the cell structure is constructed.

Although a number of different techniques already exist for productionof porous inorganic macrostructures with the desired size and shape,these techniques have a number of limitations that can affect theproperties and performance of the macrostructures during their use. Mostof these techniques require the use of a binder to give themacrostructure acceptable mechanical strength. The presence of thebinder can adversely affect certain desired properties, such as highspecific surface area and uniform chemical composition. Also, most ofthe existing binding techniques constrain the ability to tailor themacrostructure in size and shape within narrow limits. If a well definedsize is desired with a narrow particle size distribution, it is manytimes necessary and most often required, to separate desirable andundesirable macrostructures, which can lead to considerable waste duringmanufacture. The use of different types of binders can also affect thepore structure in the macrostructures and it is often necessary to finda compromise between mechanical properties and pore size. It is oftendesirable to have a bimodal pore size distribution in themacrostructures of the porous materials, in which the microporesmaintain a large specific phase interface, whereas the larger pores inthe meso- or macropore range permit transport of molecules to thesurface and, in this way, prevent diffusion limitations. Duringproduction of macrostructures using known techniques, a secondary systemof pores within the meso- and/or macropore range can be produced byadmixing a particulate inorganic material or by admixing organicmaterial (for example, cellulose fibers), which are later eliminated bycalcining. Both of these techniques, however, often produce an adverseeffect on the other properties of the resulting material.

The present invention provides a process for the production ofmacrostructures of porous inorganic materials with controlled size,shape and porosity in which it is possible to overcome or at leastmitigate one or more of the above-described problems.

SUMMARY OF THE INVENTION

One purpose of the present invention is to reduce or eliminate thedrawbacks in the known methods for production of macrostructures with anew process that permits production of these macrostructures withoutaddition of binders and with a uniform final composition. Anotherpurpose of the present invention is to provide a process, according towhich the final shape, size and size distribution of the macrostructurecan be controlled. Still another purpose of the present invention is toprovide a process according to which both the pore structure of thematerial and a secondary system of larger pores can be controlled. Afurther purpose of the present invention is to provide a process forproduction of macrostructures of porous material with good mechanicaland thermal stability.

In accordance with the present invention, there is provided compositematerial comprising a porous organic ion exchanger and a continuousthree-dimensional matrix of porous inorganic material which is presentin the three-dimensional pore structure of the porous ion organic ionexchanger. Removal of the porous ion organic ion exchanger from thecomposite material results in macrostructures having good mechanicalstrength and stability.

In another embodiment, there is provided macrostructures of porousinorganic material which can have controlled size, shape and porosityand comprise a three-dimensional network of particles of porousinorganic material.

In another embodiment, there is provided a process for preparingmacrostructures of porous inorganic material with controlled size, shapeand porosity. The process involves first producing composite materialfrom an admixture containing a porous organic ion exchanger and asynthesis mixture capable of forming the porous inorganic material. Theproduction of the composite material is carried out by converting thesynthesis mixture to the porous inorganic material. Usually, theconversion of the synthesis mixture to the porous inorganic material iscarried out under hydrothermal conditions. After formation of thecomposite material, the porous organic ion exchanger can be removed fromthe composite material to obtain the macrostructures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a schematic description of the different stages inproduction of spherical particles or thin films of porous organicmaterial according to the invention.

FIG. 2 represents adsorption-desorption isotherms measured for sphericalparticles of amorphous silica of Examples 1 and 2.

FIG. 3 and FIG. 4 show SEM micrographs, at two different magnifications,of spherical particles of the molecular sieve Silicalite 1 of Example 3.

FIG. 5 represents an X-ray diffraction pattern for spherical particlesof the molecular sieve Silicalite 1 of Example 3.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention for preparing of macrostructures ofporous organic material preferably comprises the following steps:

-   -   (a) forming a admixture comprising a porous organic ion        exchanger and a synthesis mixture capable of forming said porous        inorganic material and which occupies at least a portion of the        pore space of the porous organic ion exchanger;    -   (b) converting said synthesis mixture within the pore space of        said porous inorganic ion exchanger under hydrothermal        conditions to form said porous inorganic material; and,    -   (c) removing said porous organic ion exchanger.

The porous organic ion exchanger can be removed using techniques know topersons skilled in the art. Examples of such techniques includeoxidation processes such as calcination, and chemical removal such as bychemical destruction or chemical dissolution. Usually, the removal ofthe porous organic ion exchanger will result in macrostructures with thesize and shape of the employed organic ion exchanger.

Macrostructures refer to structures with a size that exceeds 0.01 mm inat least one dimension, preferably 0.1 mm and, more preferably, 1.0 mm.Examples of macrostructures are spherical particles, cylindricalextrudates, pellets, fibers, thin films applied to different forms ofsubstrates and other composites, in which the porous material iscombined with other types of material.

The term “average particle size” as used herein, means the arithmeticaverage of the diameter distribution of the particles on a volume basis.

The macrostructure will be porous and will comprise a three-dimensionalmatrix of particles of porous inorganic oxide. Usually, the particleswill occupy less than 75% of the volume of the macrostructures.Preferably, the particles will have an average particle size of lessthan 500 nm. The particles will be joined together and can even beintergrown. More preferably, the particles will have an average particlesize of less than 200 nm, e.g., 100 nm and will occupy less than 50% ofthe total volume of the macrostructure.

Porous inorganic materials that find particular application includecrystalline molecular sieves and mesoporous materials. Examples ofmesoporous material that find particular application include amorphoussilica, amorphous alumina, and amorphous aluminosilicates. For someapplications, it is preferable that the pore size of the mesoporousinorganic material be in the range of from about 20 Å to about 50 Å.

Molecular sieves produced by the process of the invention includesilicates, metallosilicates such as aluminosilicates and gallosilicates,and ALPO-based molecular sieves such as aluminophosphates (ALPO),silicoaluminophosphates (SAPO), metalloaluminophosphates (MeAPO), andmetalloaluminophosphosilicate (MeAPSO). Some of these molecular sieves,while not being true zeolites, are frequently referred to in theliterature as such, and this term will be used broadly below.

Molecular sieves/zeolites that find application in the present inventioninclude any of the naturally occurring or synthetic crystallinemolecular sieves. Examples of these zeolites include large porezeolites, intermediate pore size zeolites, and small pore zeolites.These zeolites and their isotypes are described in “Atlas of ZeoliteStructure Types”, eds. W. H. Meier, D. H. Olson and Ch. Baerlocher,Elsevier, Fourth Edition, 1996, which is hereby incorporated byreference. A large pore zeolite generally has a pore size of at leastabout 7 Å and includes LTL, VFI, MAZ, MEI, FAU, EMT, OFF, *BEA, and MORstructure type zeolites (IUPAC Commission of Zeolite Nomenclature).Examples of large pore zeolites include mazzite, offretite, zeolite L,VPI-5, zeolite Y, zeolite X, omega, Beta, ZSM-3, ZSM-4, ZSM-18, ZSM-20,SAPO-37, and MCM-22. An intermediate pore size zeolite generally has apore size from about 5 Å to about 7 Å and includes, for example, MFI,MEL, MTW, EUO, MTT, MFS, AEL, AFO, HEU, FER, and TON structure typezeolites (IUPAC Commission of Zeolite Nomenclature). Examples ofintermediate pore size zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22,ZSM-23, ZSM-34, ZSM-35, ZSM-385, ZSM-48, ZSM-50, ZSM-57, silicalite 1,and silicalite 2. A small pore size zeolite has a pore size from about 3Å to about 5.0 Å and includes, for example, CHA, ERI, KFI, LEV, SOD, andLTA structure type zeolites (IUPAC Commission of Zeolite Nomenclature).Examples of small pore zeolites include ZK-4, ZSM-2, SAPO-34, SAPO-35,ZK-14, SAPO-42, ZK-21, ZK-22, ZK-5, ZK-20, zeolite A, hydroxysodalite,erionite, chabazite, zeolite T, gemlinite, ALPO-17, and clinoptilolite.

The preferred molecular sieve/zeolite will depend on its use There aremany known ways to tailor the properties of the molecular sieves, forexample, structure type, chemical composition, ion-exchange, andactivation procedures. Macrostructures comprised of molecular sieveparticles do not require the presence of significant amounts ofamorphous materials to bind together the molecular sieve particles.Thus, macrostructures comprised of the molecular sieve particles cancontain less than 10% by weight of amorphous binder material based onthe weight of the microstructures. For many applications, thesemacrostructures will contain even lesser amounts of amorphous binder,e.g., 5% by weight or even less, e.g., the macrostructures can besubstantially free of amorphous binder.

When the molecular sieve produced is an crystalline metallosilicate, thechemical formula of anhydrous crystalline metallosilicate can beexpressed in terms of moles as represented by the formula:M₂/n0:W₂O₃:ZSiO₂, wherein M is selected from the group consisting ofhydrogen, hydrogen precursors, monovalent, divalent, and trivalentcations and mixtures thereof; n is the valence of the cation and Z is anumber of at least 2, preferably at least 3, said value being dependentupon the particular type of molecular sieve, and W is a metal in theanionic framework structure of the molecular sieve such as aluminum,gallium, boron, or iron.

When the molecular sieve produced has an intermediate pore size, themolecular sieve preferably comprises a composition having the followingmolar relationship:X₂O₃:(n)YO₂,wherein X is a trivalent element, such as aluminum, gallium, zinc, iron,and/or boron, Y is a tetravalent element such as silicon, tin, and/orgermanium; and n has a value greater than 10, usually from about 20 toless than 20,000, more usually from 50 to 2,000, said value beingdependent upon the particular type of molecular sieve and the trivalentelement present in the molecular sieve.

When the molecular sieve is a gallosilicate intermediate pore sizemolecular sieve, the molecular sieve preferably comprises a compositionhaving the following molar relationship:Ga₂O₃ :ySiO₂wherein y is between about 20 and about 500, typically from 20 to 200.The molecular sieve framework may contain only gallium and silicon atomsor may also contain a combination of gallium, aluminum, and silicon.

The composition of the synthesis mixture will vary according to theporous inorganic material to be produced. For example, in makingsilicalite 1 or silicalite 2, the aqueous synthesis mixture will containa source of silicon, and will usually contain a structure directingagent. When preparing an aluminosilicate zeolite, the aqueous synthesismixture will contain sources of silica and alumina and will usuallycontain a structure directing agent. When the porous inorganic materialto be produced is an ALPO-based molecular sieve, the aqueous synthesismixture will contain sources of aluminum and phosphorus, optionallysilicon and will usually contain a structure directing agent.

For the manufacture of a MFI structure type zeolite, especially ZSM-5 orsilicalite 1, the synthesis mixture is advantageously of a molarcomposition, calculated in terms of oxides, within the following ranges:

-   -   M₂O:SiO₂ 0 to 0.7 to :1 preferably 0.016 to 0.350:1    -   SiO₂:Al₂O₃ 12 to infinity:1    -   (TPA)₂O:SiO₂ 0 to 0.2:1 preferably 0 to 0.075:1    -   H₂O:SiO₂ 7 to 1000:1 preferably 9 to 300:1    -   wherein TPA represents tetrapropylammonium and M is an alkali        metal, preferably sodium or potassium, also Li, Cs and ammonia.        Other template agents may be used in these ratios.

The organic ionic exchangers used in the present invention refers toorganic porous materials with a surface charge and ion exchange capacityfor anions or cations. Preferably, the organic ionic exchangers arepolymer-based which are sometimes referred to as ion exchange resins.Polymer-based ionic exchangers are commercially available or can bereadily prepared from resins that are commercially available. Examplesof such resins include resins sold by Rohm and Haas Company under theregistered trademark Amberlyst and resins sold by the Dow ChemicalCompany under the registered trademark Dowex. These exchangers cover abroad spectrum of different cation and anion exchangers with varying ionexchange capacity, porosity, pore size and particle size. Ion exchangerswith an apparent anion exchange capacity, typically greater than about 1meg/gm of dry anion exchanger, are of special interest to the presentinvention. Macroreticular organic ionic exchangers are particularlypreferred in the practice of the present invention. By “macroreticular”as the term is commonly used in the resin art, it is generally meantthat the pores, voids, or reticules are substantially within the rangeof about 200 to about 2,000 Å. Macroreticular resins are also referredto as macroporous resins.

A preferred group of ion exchangers suitable for use in the process ofthe present invention are anion exchange resins comprisingwater-insoluble polymeric resins having attached thereto a plurality ofactive anion exchange sites. The resin generally contains sufficient ofsuch active ion exchange groups to impart thereto a concentration of ionexchange sites in the range from about 0.5 to about 12 meq/gram dryresin, typically greater than 1 meg/gram, and in some cases, preferablyfrom about 4 to about 5.5 meq/gram of dry resin.

Anion-exchange resins are characterized as either strong base or weakbase anion-exchange resins depending on the active ion-exchange sites ofthe resin. Strong base anion-exchange resins consist of polymers havingmobile monovalent anions, such as hydroxide and the like associated forexample with covalently bonded quaternary ammonium, phosphonium orarsonium functional groups or tertiary sulfonium functional groups.These functional groups are known as active sites and are distributedover the surface of the resin particle. Strong base anion-exchangeresins have the capacity to undergo ion exchange independent of the pHof the medium by virtue of their intrinsic ionic character.Macroreticular strong base anion-exchange resins in the hydroxide formare particularly preferred in the practice of the present invention.

The resin matrix of weak base anion-exchange resins contains chemicallybonded thereto a basic, nonionic functional group. The functional groupsinclude primary, secondary, or tertiary amine groups. These may bealiphatic, aromatic, heterocyclic or cycloalkane amine groups. They mayalso be diamine, triamine, or alkanolamine groups. The amines, forexample, may include alpha, alpha′-dipyridyl, guanidine, anddicyanodiamidine groups. Other nitrogen-containing basic, non-ionicfunctional groups include nitrile, cyanate, isocyanate, thiocyanate,isothiocyanate, and isocyanide groups. Pyridine groups may also beemployed.

Ion exchangers of the strongly basic type which contain quaternaryammonium groups, have been found to be particularly suited for use inthe present invention. Commercially available ion exchangers aregenerally in the form of spherical particles with a relatively narrowparticle size distribution. Organic ion exchangers with a size and shapeother than spherical, for example, fibers or flakes, however, can beproduced according to known techniques. It is also known that films oforganic ion exchangers can be deposited on different forms ofsubstrates.

The term “seeds” refers to particles, e.g., crystallites, of porousinorganic material, e.g., molecular sieves, that are capable ofinitiating crystallization of the desired porous inorganic material. Theseeds, which can be present in the synthesis mixture before itssynthesis, e.g., seeds can be added to the synthesis mixture, or can beformed in situ usually in the early stage of synthesis of the porousinorganic material and are characterized by the fact that by treatmentin of the synthesis mixture with appropriate concentration and undersuitable conditions, the seeds can be made to grow and form a continuousstructure in the pore system of the ion exchanger. Examples of suchseeds includes silicate seeds, metal silicate seeds such asaluminosilicate, borosilicate, gallosilicate, and iron silicate seeds,SAPO seeds, and ALPO seeds. Preferred seeds include olgomeric anions ofsilicates and metal silicates. The term “seeds” also includesmicrocrystals of porous inorganic material, e.g., crystals of molecularsieves with a size below 500 nm, e.g., 200 nm, and whose crystalstructure can be identified by X-ray diffraction. Microcrystals ofmolecular sieves suitable for use in the process of the presentinvention are disclosed in U.S. Pat. No. 5,863,516, which is herebyincorporated by reference.

Although the invention is not intended to be limited to any theory ofoperation, it is believed that one of the advantages of the presentinvention is that the surface of the porous organic ion exchanger canfacilitate nucleation of the synthesis mixture resulting in theformation of seeds which can subsequently grow into a porous inorganicmatrix. In line with this theory, it is believed that the surface chargeof the porous organic ion exchanger can attract seeds or seed formingmaterial onto the surface of the porous the ion exchanger. For example,anion exchange resins, which have a positive charge, can attractnegatively charged seeds such as silicate seeds, metal silicate seedsand aluminosilicate seeds.

In a second phase in production of porous macrostructures according tothe invention, the seeds formed on or bonded to the surface in theorganic ion exchanger are made to grow such as by hydrothermal treatmentin an appropriate synthesis solution. Through this growth a continuousthree-dimensional network of porous material is formed in the porestructure of the employed ion exchange structure. After this stage, theproduct is a composite material comprising two continuousthree-dimensional networks, one comprising the polymer structure of theion exchanger, and the second comprising the formed inorganic porousmaterial. Introduction of seeds can be carried out physically in aseparate stage, with a subsequent growth stage under appropriateconditions in a synthesis solution. However, it is also possible andoften advantageous not to separate these stages, but instead to directlyintroduce the ion exchanger material into a synthesis solution andexpose this to hydrothermal conditions, during which seeds are formed inor ion-exchanged from the synthesis solution to the ion exchanger, tothen grow the material into a continuous structure.

Molecular sieves are generally produced by hydrothermal treatment of asilicate solution with synthesis mixture. Hydrothermal treatment refersto treatment in aqueous solution or aqueous suspension at a temperatureexceeding 50° C., preferably exceeding 80° C. and, in most cases,exceeding 95° C. In some instances, it is preferable to carry out thehydrothermal treatment first at a lower temperature and then at a highertemperature. In the synthesis of some of the microporous molecularsieves, e.g., silicalite 1, the crystallinity can be increased when thehydrothermal treatment is carried out at in two steps. In the initialstep, the temperature is lower, e.g., 90-110° C., than the second step,e.g., 150-165° C.

The composition of the synthesis mixture and the synthesis parameters,like temperature, time and pressure, can effect the product obtained aswell as the size and shape of the formed crystals. This applies both insyntheses, in which the final product is deposited as crystals in theporous structure of an ion exchanger, and in conventional synthesis,when the final crystal size is most often much larger. The materialdeposited in the pore system of the ion exchanger is therefore dependenton the composition of the synthesis mixture and the synthesisconditions. During crystallization of macrostructures of a givenmolecular sieve according to the present invention, it is sometimesdesirable to use synthesis mixtures, which, in the absence of ionexchanger material, result in colloidal suspensions of the desiredmolecular sieve. In some instances, the ion exchanger material caninfluence the result of the synthesis.

The composite of ion exchanger and porous inorganic material obtainedafter this process can be of interest by itself in certain commercialapplications. However, for most potential areas of application it isadvantageous to eliminate the organic ion exchanger from the composite.This can occur after formation of the porous inorganic material, whichleaves behind only the porous material with a secondary pore system witha porosity and pore size caused by the structure of the employed organicion exchanger. Removal of the organic ion exchanger preferably occurs bycalcining at a temperature exceeding 400° C. The calcination can takeplace in the presence of acid, in which this material is burned tomostly carbon dioxide and water. As an alternative, the organic materialcan be removed by selective dissolution with a solvent that dissolvesthe ion exchanger, but not the inorganic material, or with selectivedecomposition of the inorganic material by means of a chemical reactionother than by an oxidation reaction.

After removal of the ion exchanger, the resulting inorganicmacrostructure is usually a replica in size and shape of the organic ionexchanger present in the admixture. This means that the possibilitiesfor controlling the size, shape and meso/macroporosity in the inorganicporous material are largely determined by the possibilities ofstructural manipulation of the properties of the ion exchanger. Thesecondary pore structure of the macrostructure will be revealedfollowing removal of the organic ion exchanger material. Themacrostructure however, can be further treated after removal from theion exchanger by deposition of porous organic materials, e.g., molecularsieves such as silicalite 1 and silicalite 2. Upon depositing theinorganic material, the secondary pore structure can be more or lesssealed and, in the extreme case, leave behind a homogeneous porousmaterial (without porosity in the meso/macropore range). This could beof interest, for example, in the production of thin films of porousstructures, for use in applications, like membranes for catalyst orseparation purposes, or in chemical sensors. It is also possible,according to a known technique, to coat the surface of themacrostructures of a given type of porous material produced according tothe invention with a thin film of another type of material, somethingthat could be of interest in a catalytic context or during use ofmacrostructures for controlled dosage of drugs or pesticides.

The porous inorganic material prepared by the process of the presentinvention can be treated to provide a more acidic form or to replace atleast in part the original metals present in the materials with adifferent cation, e.g., a Group IB to VIII Periodic Table metal such asnickel, copper, zinc, palladium, platinum, calcium or rare earth metal.

EXAMPLES

In the examples, the resulting products were evaluated by a scanningelectron microscope (SEM), X-ray diffractometry (XRD), spectroscopy andby measurements of the specific surface area and pore size distributionwith krypton or nitrogen adsorption.

Scanning electron microscope studies were conducted on samples coatedwith gold (by a sputtering technique). A scanning electron microscope ofthe Philips XL 30 type with a Lanthanum hexa-Boride emission source wasused in these studies.

X-ray diffraction studies were conducted with a Siemens D-5000 powderdiffractometer.

Nitrogen adsorption measurements to determine specific surface area andparticle size distribution were carried out with an ASAP 2010 fromMicromeritics Instruments, Inc.

Elemental analysis concerning carbon, nitrogen and hydrogen was carriedout on certain samples by means of an analytical instrument from LECOCorporation (LECO CHN-600). The particle size and particle sizedistribution for the colloidal suspensions of discrete microcrystals ofmolecular sieves used as starting material according to the process weredetermined by dynamic light scattering (ZetaPlus, BrookhavenInstruments).

Example 1

Macrostructures comprising spherical particles of porous amorphoussilica with very high specific surface area were prepared as follows:

A synthesis solution with the following composition (on a molar basis):9TPAOH:25SiO₂:480H₂O:100EtOH (TPAOH representing tetrapropylammoniumhydroxide and EtOH representing ethanol) was prepared by mixing 20.0grams of tetraethoxysilane (>98%), 34.56 grams of tetrapropylammoniumhydroxide (1.0M solution) and 5.65 grams of distilled water. The mixturewas allowed to hydrolyze in a polyethylene flask on a shaking table for12 hours at room temperature. An amount of 1.0 grams of a strongly basicanion exchange resin sold under the tradename Dowex 1X2-100 type andmanufactured by the Dow Chemical Company was added to 10 grams of thesynthesis solution. The anion exchange resin was present as sphericalparticles with a particle size range of 50-100 mesh (dry) and the ionexchange capacity of the resin was specified by the manufacturer to be3.5 mEq/g.

The mixture of ion exchanger and synthesis solution was heated in apolyethylene reactor equipped with a reflux condenser in an oil bath at100° C. for 48 hours. After this time, the ion exchanger resin particleswere separated from the solution by filtration and treated in a 0.1Mammonia solution in an ultrasound bath for 15 minutes and then separatedfrom the ammonia solution by filtration. Next, the particles were washedthree times by suspension in distilled water, followed by separation byfiltration, and then dried in a heating cabinet at 60° C. for 12 hours.Next, the particles were calcined at 600° C. in air for 4 hours, afterheating to this temperature at a rate of 10° C./min.

The resulting material consisted of hard, solid, white sphericalparticles with a size distribution identical to that in the employed ionexchanger. Elemental analysis showed that the particles were almostentirely free of carbon, hydrogen and nitrogen, which showed that theion exchanger had been completely eliminated in the calcining stage.

X-ray diffractometry also showed that the material was completelyamorphous. The particles were also analyzed by nitrogen adsorptionmeasurements at the boiling point of nitrogen to determine the specificsurface area, the adsorption isotherm and pore size distribution of theporous amorphous silica. The specific surface area was calculated fromthe adsorption data according to the BET equation as 1220 m²/g. Therecorded isotherm is shown in FIG. 2 and was of type I, which is typicalof porous materials. Calculation of the pore size distribution by theBJH method (desorption isotherm) showed that a very small fraction(about 20 m²/g) of the total specific surface area of the material wasfound in pores in the mesopore range (diameter >20 Å). The average porediameter was calculated at 9.5 Å by the Horvath-Kawazoes method.

Example 2

Macrostructures comprising spherical particles of amorphous aluminumsilicate with high specific surface area in pores in both the micro- andmesopore range were prepared as follows:

25 grams of a synthesis solution with the molar composition:2.4Na₂O:1.0TEACl:0.4Al₂O₃:10SiO₂:/460H₂O (TEACI representingtetraethylammonium chloride) were added to 2.0 grams of a strongly basicion exchanger sold under the tradename Dowex MSA-1 and manufactured bythe Dow Chemical Company (particle size 20-50 mesh and [dry] ionexchange capacity of 4 mEq/g) in a polyethylene reactor. The synthesismixture was prepared by first dissolving 0.75 grams sodium aluminate(50.6 wt % Al₂O, 36 wt % Na₂O) in 35 grams of a 1M NaOH solution at 100°C. This solution was then added to a mixture of 40 grams distilledwater, 1.66 grams TEACI and 15 grams silica sol (Bindzil 40/130, EkaChemicals AB, solids content 41.36 wt %, 0.256 wt % Na₂O) duringagitation for 2 hours. The mixture of ion exchanger and synthesissolution was treated in a polyethylene reactor equipped with a refluxcondenser in an oil bath at 100° C. for 48 hours. After this time, theion exchanger particles were separated from the solution by filtrationand treated in a 0.1M ammonia solution in an ultrasound bath for 15minutes and then separated from the ammonia solution by filtration. Theparticles were finally washed three times by suspension in distilledwater, followed by separation by filtration, and then dried in a heatingcabinet at 60° C. for hours. Next, the particles were calcined at 600°C. in air for 4 hours, after heating to this temperature at a rate of10° C./min.

Visual inspection and analysis with a scanning electron microscopeshowed that the resulting material consisted of very hard, solid, whitespherical particles with size distribution identical to that in theemployed ion exchanger. Elemental analysis showed that the particleswere almost entirely free of carbon, hydrogen and nitrogen, which showedthat the ion exchanger material had been completely eliminated in thecalcining stage.

X-ray diffractometry showed that the material was completely amorphous.The particles were further analyzed by nitrogen adsorption measurementsat the boiling point of nitrogen to determine the specific surface area,adsorption isotherms and pore size distribution. The specific surfacearea was calculated from the adsorption data according to the BETequation as 594 m²/g. The recorded isotherm is shown in Example 2 andwas of type IV. Calculation of the pore size distribution by the BJHmethod (desorption isotherm) showed that a relatively large percentageof the total (cumulative) pore volume (about 65%) was found in pores inthe mesopore range (radius >20 Å).

Example 3

Macrostructures comprising spherical particles of Silicalite 1 wereprepared as follows:

14.3 grams of a synthesis solution with the molar composition:9TPAOH:25SiO₂:480H₂O:100EtOH were added to 1.0 grams of a macroporousstrongly basic ion exchanger sold under the tradename Dowex MSA-1 andmanufactured by the Dow Chemical Company (particle size 20-50 mesh[dry]; ion exchange capacity: 4 mEq/g). The synthesis mixture wasprepared as described in Example 1. The mixture of ion exchanger andsynthesis solution was heated in a polyethylene reactor equipped with areflux condenser in an oil bath at 100° C. for 48 hours. After thistime, the ion exchanger particles were separated from the solution andthe material was crystallized in the bulk phase by filtration andtreated in a 0.1M ammonia solution in an ultrasound bath for 15 minutes,whereupon they were separated again by filtration. Next, the particleswere washed three times by suspension in distilled water, followed byseparation by filtration, and then dried in a heating cabinet at 60° C.for 12 hours. Next, the particles were calcined at 600° C. in air for 10hours, after heating to this temperature at a rate of 1° C./min.

Visual inspection and scanning electron microscopy revealed that theresulting material consisted of very hard, solid (homogeneous), whitespherical particles with a size distribution identical to that in theemployed ion exchanger. The primary particles making up the spheres hada size of about 100 nm. Also, the primary particles on the surface ofthe spheres was similar to the particles in the interior of the spheres.Elemental analysis showed that the particles were almost entirely freeof carbon, hydrogen and nitrogen, which showed that the ion exchangermaterial was fully eliminated in the calcining stage. FIGS. 3 and 4 aretwo SEM photographs of the material taken at two differentmagnifications. FIG. 3 taken at the lower magnification shows thespherical character of the particles, whereas FIG. 4 taken at highmagnification shows the presence of small primary particles (primarycrystals) with a size of about 100 nm. X-ray diffractometry revealedthat the material is crystalline and consists of Silicalite 1, but thatit also contains a percentage of amorphous material. An X-raydiffraction pattern for this sample is shown in FIG. 5. Analysis withnitrogen adsorption gave a specific surface area of 438 m²/g and showedthat most of the pore volume was found in micropores with an averagepore diameter of 6 Å, calculated according to the Horvath-Kawazoesmethod.

Silicalite 1 was prepared using the same procedures as described above,except that the hydrothermal treatment was carried out at differenttemperatures.

In the first Silicalite 1 preparation, the hydrothermal treatmenttemperature was 165° C. Scanning electron microscopy showed that thesurface of the spheres of the resulting product were overlaid withcrystals of MFI-type zeolite and had a size up to 500 nm. The inner partof the spheres was less homogeneous and agglomerates of small particlescould be distinguished.

In the second preparation, the hydrothermal treatment was carried out intwo steps. The temperature of the first step was 100° C. and thetemperature of the second step was at 165° C. The resulting spheres werehighly crystalline which indicates that the degree of crystallinity canbe increased by a second hydrothermal treatment at a higher temperature.

Example 4

Macrostructures comprising spherical particles of ZSM-5 were prepared asfollows:

15 grams of a synthesis solution with the molar composition:0.35Na₂O:9TPAOH:0.25Al₂O₃:25SiO₂:405H₂O were added to 1.0 grams of amacroporous strongly basic anion exchanger sold under the tradenameDowex MSA-1 and manufactured by the Dow Chemical Company (particle size20-50 mesh [dry]; ion exchange capacity: 4 mEq/g). The synthesis mixturewas prepared by first dissolving 0.408 grams of aluminum isopropoxide in10 grams of 1.0M tetrapropylammonium hydroxide. Another solution wasprepared by dissolving 6.0 grams freeze-dried silica sol (Bindzil30/220, 31 wt % SiO₂, 0.5 wt % Na₂O Eka Chemicals, AB) in 26 grams 1.0MTPAOH at 100° C. The two solutions were mixed under agitation for 30minutes. The mixture of ion exchanger and synthesis solution was heatedin a polyethylene reactor equipped with a reflux condenser in an oilbath at 100° C. for 20 days. After this time, the ion exchangerparticles were separated from the solution and the material wascrystallized in the bulk phase by filtration and treated in a 0.1Mammonia solution in an ultrasound bath for 15 minutes, and thenseparated again by filtration. Next, the particles were washed threetimes by suspension in distilled water, followed by separation byfiltration, and then dried in a heating cabinet at 60° C. for 12 hours.Next, the particles were calcined at 600° C. in air for 10 hours, afterheating to this temperature at a rate of 1° C./min.

Visual inspection and analysis with a scanning electron microscopeshowed that the product largely consisted of white, solid particles witha size and shape identical to that of the employed ion exchanger. Arelatively large fraction of the product, however, was shown to consistof particles with roughly the same size as the employed ion exchanger,but with a more irregular shape. SEM analysis at high magnificationshowed that the particles consisted of intergrown crystals with amorphology typical of MFI structures and with a size of about 1 μm.X-ray diffractometry showed that the particles consisted of zeoliteZSM-5 and a relatively large fraction of amorphous material. Thespecific surface area was measured by nitrogen adsorption at 612 m²/g.

Example 5

Macrostructures comprising spherical particles of zeolite A wereprepared as follows:

18.0 grams of a synthesis solution with the molar composition:0.22Na₂O:5.0SiO₂:Al₂O₃:8TMA₂O:/400H₂O were added to 1.0 grams of astrongly basic anion exchanger sold under the tradename Dowex MSA-1 andmanufactured by the Dow Chemical Company. The synthesis mixture wasprepared by first dissolving 1.25 grams of aluminum isopropoxide and 9.0grams tetramethylammonium hydroxide pentahydrate in 0.90 grams of 1.0Msolution of NaOH and 3.0 grams water under agitation for 2 hours. Thissolution was added to a mixture of 3.0 grams silica sol (Bindzil 30/220,31 wt % SiO₂, 0.5 wt % Na₂O Eka Chemicals, AB) and 12 grams of distilledwater and the resulting solution was agitated for 3 hours. The mixtureof ion exchanger and synthesis solution was heated in a polyethylenereactor equipped with a reflux condenser in an oil bath at 100° C. for10 hours. After this time, the ion exchanger particles were separatedfrom the solution and the material was crystallized in the bulk phase byfiltration and treated in a 0.1M ammonia solution in an ultrasound bathfor 15 minutes, and then separated again by filtration. Next, theparticles were washed three times by suspension in distilled water,followed by separation by filtration, and then dried in a heatingcabinet at 60° C. for 12 hours. Next, the particles were calcined at600° C. in air for 10 hours, after heating to this temperature at a rateof 1° C./min.

Visual inspection and analysis by scanning electron microscopy showedthat the product largely consisted of light brown, solid particles. Thesize of the particles was smaller than the employed ion exchanger. Asmaller fraction of the product consisted of fragmented particles. SEMat high magnification showed that the particles are homogeneous and areconstructed from intergrown primary particles with a size up to about300 nm. X-ray diffractometry showed that the resulting materialcontained zeolite A and a certain amount of amorphous material. Nitrogenadsorption measurements gave a specific surface area (according to theBET equation) of 306 m²/g and indicated the presence of both micro- andmesoporosity.

Example 6

Macrostructures comprising spherical particles of zeolite Beta wereprepared as follows:

15 grams of a synthesis solution with the molar composition:0.35Na₂O:9TEAOH:0.5Al₂O₃:25SiO₂:295H₂O were added to 1.0 grams of astrongly basic anion exchanger sold under the tradename Dowex MSA-1 andmanufactured by the Dow Chemical Company. The synthesis mixture wasprepared by dissolving 0.81 grams aluminum isopropoxide in 6.0 gramstetraethylammonium hydroxide (TEAOH, 20% solution) at 100° C. Thissolution was added to a solution of 6.0 grams freeze-dried silica sol(Bindzil 30/220, 31 wt % SiO₂, 0.5 wt % Na₂O Eka Chemicals, AB)dissolved in 20 grams of TEAOH (20% solution) and the resulting solutionwas agitated for 30 minutes. The mixture of ion exchanger and synthesissolution was heated in a polyethylene reactor equipped with a refluxcondenser in an oil bath at 100° C. for 8 days. After this time, the ionexchanger particles were separated from the solution and the materialwas crystallized in the bulk phase by filtration and treated in a 0.1Mammonia solution in an ultrasound bath for 15 minutes, whereupon theparticles were separated again by filtration. The particles were finallywashed three times by suspension in distilled water, followed byseparation by filtration, and then dried in a heating cabinet at 60° C.for 12 hours. Next, the particles were calcined at 600° C. in air for 10hours, after heating to this temperature at a rate of 1° C./min.

Visual inspection, as well as analysis with a scanning electronmicroscope, showed that the product largely consisted of hard, white,solid particles with a size and shape identical to that of the employedion exchanger. SEM analysis at high magnification shows that thematerial is constructed of intergrown primary particles with a size ofabout 80 nm. X-ray diffractometry showed that the particles containedzeolite Beta as the only crystalline phase. The specific surface areacalculated with the BET equation, based on nitrogen adsorption data, was580 m²/g.

Example 7

A film of Silicalite 1 was built upon the surface of a macrostructure ofSilicalite 1 produced according to Example 3 as follows:

10.0 grams of synthesis solution with the composition and preparationaccording to Example 3 were added to 0.20 grams of calcined productproduced according to Example 3. This mixture was heated at 100° C. in apolyethylene reactor equipped with a reflux condenser for 48 hours.After this time, the particles were separated from the solution and thematerial was crystallized in the bulk phase by filtration and treated ina 0.1M ammonia solution in an ultrasound bath for 15 minutes, whereuponthey were separated again by filtration. The particles were finallywashed three times by suspension in distilled water, followed byseparation by filtration, and then dried in a heating cabinet at 60° C.for 12 hours. Part of the material was calcined at 600° C. for 10 hours,after heating to this temperature at a rate of 1° C./min. X-raydiffraction measurements on the calcined sample revealed that the samplecontained Silicalite 1 as the only crystalline phase. Scanning electronmicroscopy detected an outer layer of Silicalite 1 on the surface of theparticles, a layer that synthesis had built up from about 300/-nm largeprimary particles. The specific surface area was determined for theuncalcined sample as 92 m²/g, whereas the corresponding value measuredfor the calcined sample was 543 m²/g. The difference in the surfacebefore and after calcining indicates that the outer shell of Silicalite1 effectively encloses the open pore system in the original particles.

1. Macrostructures comprising a three-dimensional matrix of particlescomprising porous inorganic material and having an average particle sizeof less than about 500 nm.
 2. The macrostructures recited in claim 1,wherein said particles have an average particle size of less than 200 nmand occupy less than 75% of the total volume of the macrostructure. 3.The macrostructures recited in claim 1, wherein said porous inorganicmaterial is mesoporous inorganic material.
 4. The macrostructuresrecited in claim 3, wherein said mesoporous inorganic material isselected from the group consisting of silica, aluminum silicate, andalumina.
 5. The macrostructures material recited in claim 1, whereinsaid porous inorganic material is comprised of molecular sieve.
 6. Themacrostructures recited in claim 5, wherein the structure type of saidmolecular sieve is selected from the group consisting of LTL, FAU, MOR,*BEA, MFI, MEL, MTW, MTT, MFS, FER, and TON.
 7. The macrostructuresrecited in claim 5, wherein said molecular sieve is selected from thegroup consisting of zeolite L, zeolite X, zeolite Y, mordenite, zeolitebeta, ZSM-5, ZSM-11, ZSM-22, silicalite 1 and silicalite
 2. 8. Themacrostructures recited in claim 6, wherein said particles have anaverage particle size of less than 100 nm.
 9. The macrostructuresrecited in claim 8, wherein said particles occupy less than 50% of thetotal volume of said microstructures. 10-44. (canceled) 45.Macrostructures prepared by the process recited in claim 17.